X-ray sources refer to apparatuses for generating x-rays, and generally include a x-ray tube, power & control system, and auxiliary devices such as cooling and shielding devices. The core device is the x-ray tube which is generally formed of a cathode, an anode, and a glass or ceramic case. The cathode may be made of a directly-heated spiral tungsten filament. In operation, a current flows through the cathode, and the cathode is heated to an operation temperature of about 2000K, and generates thermally-emitted electron beam currents. The cathode is surrounded by a metal hood in which a groove is opened at the front end. The metal hood enables the electrons to be focused. The anode may be made of a tungsten target mosaicked in an end surface of copper plate. There is a high voltage of hundreds of thousands volts between the anode and the cathode in operation. The electrons generated at the cathode are accelerated and travel to the anode under the electric field, and bombard the surface of the target, thereby generating x-rays.
X-rays are widely used in various fields including industrial non-destructive inspection, safety inspection, medical diagnosis, and treatment. In particular, x-ray perspective imaging apparatuses utilizing the high penetrating ability of x-rays play an important role in various aspects of people's daily life. In the past such apparatuses include film-type plane perspective imaging apparatuses. Current advanced apparatuses include digitalized, multi-view, high-resolution stereo imaging apparatuses, such as CT (Computed Tomography) which can obtain high-resolution 3-dimensional graphics or slice images, and have become an advanced and sophisticated application.
In many CT apparatuses (including CTs for industrial flaw detection, luggage or article safety inspection, medical diagnosis, and the like), an x-ray source is generally placed at one side of a subject article, and detectors are placed at the other side of the subject article for receiving the rays. When penetrating the subject article, the intensity of the x-rays will change with the thickness, density and the like of the subject article. The intensity of the x-rays received by the detectors implies information about the composition of the subject article from a certain view angle. If the locations of the x-ray source and the detector are changed around the subject article, composition information can be obtained from different view angles. The perspective image of the subject article can be obtained by performing reconstruction based on the obtained information through computer systems and software algorithms. In the existing CT apparatuses, the x-ray source and the detector are positioned on a circular slip ring surrounding the subject. In operation, an image for one section along the thickness of the subject is obtained for each loop the x-ray source and the detector move along the circular slip ring. Such an image is called a slice. Then, the subject article is moved along the thickness direction to obtain a sequence of slices. These slices are combined to show a fine 3D structure of the subject article.